diff --git a/src/cascadia/TerminalSettingsModel/ActionArgs.h b/src/cascadia/TerminalSettingsModel/ActionArgs.h
index f5bb64e1b0..929a4cfaab 100644
--- a/src/cascadia/TerminalSettingsModel/ActionArgs.h
+++ b/src/cascadia/TerminalSettingsModel/ActionArgs.h
@@ -768,38 +768,37 @@ namespace winrt::Microsoft::Terminal::Settings::Model::implementation
         }
         uint32_t GetArgCount()
         {
-            if (_ContentArgs)
-            {
-                if (const auto newTermArgs = _ContentArgs.try_as<NewTerminalArgs>())
-                {
-                    return newTermArgs->GetArgCount() + gsl::narrow<uint32_t>(GetArgDescriptors().Size());
-                }
-            }
             return gsl::narrow<uint32_t>(GetArgDescriptors().Size());
         }
         winrt::Windows::Foundation::Collections::IVectorView<Model::ArgDescriptor> GetArgDescriptors()
         {
             static const auto thisArgs = INIT_ARG_DESCRIPTORS(SPLIT_PANE_ARGS);
-            auto contentArgs = _ContentArgs.as<NewTerminalArgs>()->GetArgDescriptors();
 
             // Merge into a new vector
             std::vector<Model::ArgDescriptor> merged;
-            merged.reserve(thisArgs.Size() + contentArgs.Size());
 
             for (const auto desc : thisArgs)
             {
                 merged.push_back(desc);
             }
-            for (const auto desc : contentArgs)
+
+            if (_ContentArgs)
             {
-                merged.push_back(desc);
+                if (const auto newTermArgs = _ContentArgs.try_as<NewTerminalArgs>())
+                {
+                    auto contentArgs = newTermArgs->GetArgDescriptors();
+                    for (const auto desc : contentArgs)
+                    {
+                        merged.push_back(desc);
+                    }
+                }
             }
 
             return winrt::single_threaded_vector(std::move(merged)).GetView();
         }
         IInspectable GetArgAt(uint32_t index)
         {
-            const auto additionalArgCount = gsl::narrow<uint32_t>(GetArgDescriptors().Size());
+            const auto additionalArgCount = INIT_ARG_DESCRIPTORS(SPLIT_PANE_ARGS).Size();
             if (index < additionalArgCount)
             {
                 X_MACRO_INDEX_BASE();
@@ -813,7 +812,7 @@ namespace winrt::Microsoft::Terminal::Settings::Model::implementation
         }
         void SetArgAt(uint32_t index, IInspectable value)
         {
-            const auto additionalArgCount = gsl::narrow<uint32_t>(GetArgDescriptors().Size());
+            const auto additionalArgCount = INIT_ARG_DESCRIPTORS(SPLIT_PANE_ARGS).Size();
             if (index < additionalArgCount)
             {
                 X_MACRO_INDEX_BASE();
diff --git a/src/cascadia/TerminalSettingsModel/ActionArgsMagic.h b/src/cascadia/TerminalSettingsModel/ActionArgsMagic.h
index 06718afc37..0f99729a50 100644
--- a/src/cascadia/TerminalSettingsModel/ActionArgsMagic.h
+++ b/src/cascadia/TerminalSettingsModel/ActionArgsMagic.h
@@ -89,10 +89,10 @@ struct InitListPlaceholder
     &&(otherAsUs->_##name == _##name)
 
 #define X_MACRO_INDEX_BASE() \
-    constexpr auto X_MACRO_INDEXED_BASE__ = __COUNTER__ - 1
+    constexpr auto X_MACRO_INDEXED_BASE__ = __COUNTER__
 
 #define X_MACRO_INDEX() \
-    (__COUNTER__ - X_MACRO_INDEXED_BASE__)
+    (__COUNTER__ - X_MACRO_INDEXED_BASE__ - 1)
 
 // getter and setter for each property by index
 #define GET_ARG_BY_INDEX(type, name, jsonKey, required, typeHint, ...) \